Wednesday, March 19, 2014

Winnipeg snowfall - by the numbers

It's been a snowy winter in Winnipeg this year. Snowfall started in mid November and has not quit, with persistent cold making the snow pile up to heights we haven't seen in a while. Surely this has to be one of the snowiest winters on record for Winnipeg, right? Well, not really. As of March 18th, our total snowfall this winter has been 151 cm (since October 1st) That's well above the normal seasonal snowfall of 114 cm that usually falls in Winnipeg between October and May (based on 1981-2010 average for Winnipeg airport) And we still have a good 4-6 weeks of potential snowfall left this season to add to the total.

But as you can see from the table on the left, we still have a ways to go to even get in the top 10 snowiest winters of all time in Winnipeg, never mind the snowiest ever. In 140 years of records, only 7 winters have cracked the 200 cm mark, with the snowy winter of 1955-56 topping the list at a whopping 252.6 cm, over twice the normal snowfall for the city. Most recently, the winter of 1996-97 has been the last winter to crack the 200 cm mark, thanks in large part to a record April blizzard of 48 cm that led to the "Flood of the Century" that spring. So although we still can get some good snowfalls between now and May, we'd have to get at least 60 cm over the next month to crack the top 5 snowiest winters in the city.

Looking at a graph of winter snowfall in Winnipeg since 1873 reveals some interesting observations. Most notable is how erratic Winnipeg snowfall is from year to year, with wild swings from well above "normal" to well below. In fact, it's tough to say what "normal" is, since snowfall varies so much every winter. One way to define "normal" is to look at a longer term average. Looking at the 30 year running average (red line), one can see that snowfall has averaged roughly 125 cm for much of Winnipeg's history since 1873. That average started to dip in the 1970s and 1980s with several below normal snow seasons during that time. As a result, our 30 year running average dipped to a low of 110 cm by the 1990s. Since then, average snowfall has been trending up again, with a trend towards that 125 cm average thanks to the last few winters. Perhaps this is nature's way of reverting back to more typical snowfall amounts for this part of the world.

Graph of winter season snowfall in Winnipeg since 1873Red line shows 30 year running average (cm)

The graph also shows another interesting tidbit. The least snowy winter in Winnipeg was way back in 1877-78, during Winnipeg's warmest winter on record. Only 31 cm of snow fell that entire winter, during the "year without a winter" that was a result of an unusually strong El Nino that year that had worldwide impacts on weather, rainfall and crops. December 1877 was virtually snowfree in Winnipeg (only 0.5 cm the whole month) and no month that entire winter exceeded 8 cm of total snowfall. Incredible. (*NOTE: Some recent information suggests that Winnipeg may have experienced a significant snowfall later that spring on May 2 1878. In a Department of Transport study on the "Climate of Winnipeg" (Labelle, Brown, and Hasinoff, June 7 1966), it notes that the heaviest May snowfall on record in Winnipeg was 10.7 inches (27.2 cm) on May 2 1878. Officially in the digitized climate archives online, snowfall for Winnipeg on that date is listed as only 1.8 cm, or 0.7 inches. It's possible the data was incorrectly entered into the climate database as 0.7" instead of 10.7". Note that the nearby St Andrews climate site recorded 12" of snow (30 cm) on May 2-3rd 1878, so the potential is there that Winnipeg had much heavier snow that day than the current archive shows. I will update this info if and when I hear more.)

One last but important note. Snowfall observations are no longer taken at Winnipeg airport which was the official source for snowfall observations in the city since 1938. (St John's College took snowfall observations in Winnipeg between 1873-1938) Due to automation and a change in observing responsibilities, snowfall records at the airport stopped in 2007. Since then, snowfall readings for Winnipeg have been based on snowfall observations taken from my Charleswood observing station, an official climate station with Environment Canada. I take two snowfall readings a day from October to May, including snow depth, and send the reports to Environment Canada who archive them in their climate database. Snowfall readings at my site will not always be representative of snowfall at the airport, but at least we have some record of snowfall for the city, in the absence of official snowfall data from Winnipeg airport.

11 comments:

Hi Rob, great blog write up. You made note of the 48cm of snow that fell in April of 1997 in that big blizzard. I heard someone tell me one time, that areas in Southeastern Manitoba got close to 80cm with that blizzard. I just can't find anything on the internet with snowfall amounts for that storm...

>> Anonymous said... Rob the WINNIPEG 'A' climate station gives snowfall depths. Right now its giving a depth of 30 cm.

Yes, that's correct. However, that is an automated snowdepth sensor that measures the depth of snow with sound waves (sonic snow sensor). No human observation. As such, it is susceptible to errors due to drifting or blowing snow. Not as good as a human observation, but it's better than nothing.

>> Anonymous said... Hi Rob, great blog write up. You made note of the 48cm of snow that fell in April of 1997 in that big blizzard. I heard someone tell me one time, that areas in Southeastern Manitoba got close to 80cm with that blizzard. I just can't find anything on the internet with snowfall amounts for that storm...

Do an "advanced search", and input April 5 1997, for within 100 or 200 km of the lat/lon coordinates of 50N, 97W. That will give you a list of all EC's climate stations over SE MB, which will give you snowfall amounts during that event.

http://climate.weather.gc.ca/advanceSearch/searchHistoricData_e.html

I wasn't here for that storm, so I'm not sure about the overall totals, but I do know it was a 4 day storm with lots of ice pellets as well that contributed to high melted water values (bad news for the flood)

Rob Do these numbers include significant snowfall amounts in Oct 49 and April May of 1950 in your total. !950 s flood crest occurred or at least the second crest, the 3rd week of may. My records show 129.8 mm of precip after April 1 before the crest with approx half snow (50cm)Also over 16 mm in October 49 of snow and 128 of rain. I use approx as there are at least 3 different ways of converting snow to precip in use back then.In 96-97 the records I had indicated there was even more precip south of Winnipeg.. Morris and Emerson? and Carman I believe but I don't know how much was snow?Don

Snow is back in the forecast tomorrow night, as a clipper system from Saskatchewan dives into North Dakota. Bulk of the snow expected over Riding Mtns and SW MB, where 5-10 cm is possible.. with lesser amounts of 3-5 cm for Winnipeg. NAM model has been more aggressive on amounts for Winnipeg with 5-8 cm, so there's the potential for slightly higher amounts for us if system tracks further east. Something to keep an eye on.. but at this point bulk of snow expected south and west of Winnipeg.

Yeah, not a nice start to spring.. but then, what else would you expect this year? Relentless invasions of Arctic air are not stopping with the onset of the vernal equinox. But at least those few days of sunny seasonable weather we do get feel awfully nice.

As for tonight's system, models are bringing the swath of heaviest snow from the Brandon area through the southern RRV into SE MB, with Winnipeg on the northern edge of the heaviest snow. Still looks like a 2-5 cm event for us, but heavier amounts of 5-10 cm won't be that far way to our south. As noted. those winds will be picking up for the north overnight into Thursday morning with gusts to 70 or 80 km/h possible. That will make for some nasty conditions with blowing and drifting snow in open areas.. especially south of the city.

Great blog, Rob! Apropos of this post, maybe we perceive this winter as having abnormally high snowfalls because of the sheer accumulation... we've not had any significant mid-winter melts so pretty much all of that 150+cm of snow we've gotten since Nov. is still on the ground right now.